High-pressure and high-temperature lubricant



Aug. 10, 1937. v. R. ABRAMS ET AL.

HIGH PRESSURE AND HIGH TEMPERATURE LUBRICANT v Filed Aug. 15, 1954 loo, 000

um m, w A w Patented Aug. 10,1193? UNITED STATES PATENT OFFICE HIGH-PRESSURE AND HIGH-TEMPERA- TURE LUBRICANT poration of Georgia Application August 15, 1934, Serial No. 740,004

21 Claims.

This invention relates to methods of lubrication and lubricants adapted for high-pressure and for high-temperature use; and a particular object of the invention is to provide a mode of lubrication and type of lubricant having exceptional Value in the extreme-pressure range.

At the present time and for some time past there has been great demand by the automotive and allied industries for lubricants which would l0 make possible the use of modern gear designs.

The tooth strength and surface hardness of available metals would permit of the successful use of much smaller and lighter gears, and, hence, the load limit at present is imposed by the loadcarrying capacity of available lubricants and the problem is that of obtaining lubricants which will stand extreme pressures without producing undue wear or exhibiting other undesirable properties.

Likewise, there is an unmet demand for satisfactory higher load-carrying lubricants for use in lubricating roller and ball bearings, which because of the small bearing contact surfaces present high unit area pressure relative to the total load. Metallurgical developments have given rise to a great demand for improved lubricants which will make possible the successful use of smaller and lighter designs, as, for example, in free-wheeling devices and transmissions.

These and other demands have given rise to a very active search' for better extreme-pressure lubricants, commonly known as E. P. lubricants. While considerable progress has been made, there is today no lubricant known in the art which can be said to measure up to the standards sought.

Even in the relatively low pressure field there is a great demand for better lubrication at low speeds and at high temperatures.

Broadly speaking, there are four modes of lubrication recognized in the art:

(a) Fluid-film lubrication occurs when the viscosity of a uid medium interposed between the bearing surfaces is sufficient to prevent metal to metal rubbing. The maximum pressure per unit area which can be withstood by such lms is directly dependent upon the existing viscosity of the medium in the zone of greatest pressure; and hence is limited thereby. Most iluid or plastic lubricants, such as mineral oils and greases, rapidly decrease in viscosity with increase of temperature, and the viscosity drops to a very low point when a moderately elevated temperature has been reached. High bearing pressures necessarily produce high local temperatures, with the result that such a lubricant becomes ineffective at high pressures due to the low degree of viscosity exist ingin thehigh pressure zone, notwithstanding that the lubricant may have a, high viscosity at the lower temperatures existing outside of said zone. 'I'he failure of these lubricants at high pressure is not due to the fact that plastic or highly viscous media cannot sustain extremely high unit area loads, but is caused by the inability of the particular lubricant to maintain an adequate viscosity in the highest pressure zone existing between the bearing surfaces. This distinction has not been fully appreciated by those skilled in the art.

Mineral oil lubricants have an upper limit of vload-carrying capacity of about 6,000 lbs. per

sq. inch, but cannot be said to be satisfactory for actual use when the pressure much exceeds 1,000 lbs. per sq. inch'.

(b) Boundary-layer lubrication occurs when the lubricant or lubricant base is of such a nature as to be adsorbed -at the metallic bearing surfaces, producing a minute lubricant layer which resists rupture due to the tenacity with which it is held to the metallic surfaces and to its resistance to internal shear. This characteristic of a lubricant is often referred to as greasiness. Oleic acid is an example of a lubricant base which is often added to mineral oils for the purpose of enabling the oil to lubn'cate at lhigher pressures, and it is supposed that its effectiveness is due to the formation of a boundary or surface layer of oleic acid molecules oriented and held perpendicularly to the metallic surface. Various polar substances have been proposed and used.

The present upper limit of stable load-carrying capacity of practical lubricants of this type is about 15,000 lbs. per sq. inch under extreme conditions of temperature and total load, and since a great deal of development Work has been done and the raising of the limit by as much as 5,000 pounds regarded as a marked achievment, it is doubtful if a much higher order of magnitude is possible.

(c) Contamination-nlm lubrication is s imilar to boundary-layer lubrication, and occurs when the lubricant contains or yields a substance which combines chemically with the bearing metal to form a lm which contaminates the bearing surfaces and thus prevents welding or seizing, and which preferably offers a high resistance to rupture. Chlorinated and sulfurized oils, containing chlorine or sulphur in available reactive form, are examples of this type of lubricant. A disadvantage of this type is that substantial corrosion and wear of the bearing surfaces is produced at high pressures and temperatures, with the result that even though quite high unit area bearing pressures can be sustained momentarily, the high rate of wear at extreme-pressures makes them generally unsuitable for such use. The present,

soft to exert a polishing rather than a grinding action.v Graphite and talc are examples of this type of lubricant material. While solid particles are capable of producing satisfactory lubrication at quite high pressures, there are certain practical disadvantages which render lubricants of this type undesirable for many uses. specifications for free-wheeling transmission lubricants forbid the presence of fillers, such as talc and graphite (S. A. E. Handbook, 1933 Ed., page 436):

Many types of lubricants, or lubricant mixtures, exhibit several of the above-mentioned lubrication functions in combination. A good example of this is a suspension of flowers of sulfur in a liquid vehicle, such as is described in Patent No. 1,913,300, issued June 6, 1933, to V. R. Abrams. In the lower pressure zones between a pair of bearing surfaces the liquid vehicle will be suiiiciently viscous to sustain the load by fluid-film lubrication, and the sulfur particles may also exert solid-particle lubrication. In the highest pressure zones the existing temperatures will cause the sulfur to liquefy to afford effective iiuid-film lubrication at quite high temperatures, and a sulfide film may be produced on one or both of the surfaces to afford contamination-film lubrication. Sulfur in free or availably reactive form produces marked bearing wear under high pressures, and hence lubricants containing sulfur in such form are not capable of sustaining high bearing pressures without producing undue wear, and for this reason are not capable of stably sustaining extreme pressures.

The foregoing summary of the present general state of the art has been given in order that the full importance of our invention may be appreciated. It may fairly be said that a stable loadcarrying capacity of about 15,000 pounds per square inch under extreme conditions, and about 20,000-30,000 pounds per square inch under moderate conditions, represents the maximum at present obtainable with lubricants; other than yours, which are suitable for general use. While certain llubricants are capable of carrying heavier loads,

they cannot be said to exceed this capacity either because the load can only be carried for a short period of time or because excessive wear is produced; or because they have other undesirable properties, such as exist in the case .of graphite mentioned above.

The type of lubricant which' we have developed is exceptional'in that it is characterized by having a stable load-carrying capacity in excess of about 30,000 pounds per square inch which in some cases may be as high as 75,000 pounds per square inch, or higher; without producing appreciable bearing wear, both under ordinary and extreme lubricating conditions. 'I'he load-carrying capacity given as illustrative represents a concant compositions.

The S. A. E.

servative figure which'is much less than th'e load which can be safely carried with attendant wear,

or for vshort periods of time, by many of our lubri- Tests indicate that the loadcarrying capacity just prior to seizure may be at least several times as great.

The nature of our type of lubricant, and its behavior under various conditions, will be made evident as the description progresses.

The fundamental conception which we have, and which is the basic idea back of our invention, is that of employing as the primary lubricant media finely divided non-colloidal particles (by which is meant particles of greater than colloidal size) of organic material which at high temperatures possess a substantial viscosity and capability of highly viscous or plastic ow under pressure. These particles may either be solid at room temperature or capable of highly viscous or plastic flow, the essential thing being the foregoing characteristics at high temperatures, namely, a high resistance to ilow under pressure. Very finely divided particles, approaching colloidal size, or particles large enough to be visible to the naked eye, and those of intermediate size, may all be used.

In order to introduce these particles into the lubrication zone, we employ a mobile, more or less liquid, carrying medium or Vehicle in which the particles are distributed and in which they are insoluble both at room and high temperatures. This combination of particles and carrying medium constitutes a lubricant which can be readily employed and which is able to maintain exceptionally high bearing pressures, notwithstanding that the carrying medium has a low or der of carrying capacity.

In preferred types of lubricant mixtures the particles may be of such kind as to be insoluble in the vehicle and non-melting at high temperatures closely approaching or equal to the decomposition point of the particles.

Our conception of the mode of lubrication which occurs when our type of lubricant is employed is as follows: The lubricant particles serve as yieldable flowable cushions between the bearing surfaces and because of their relatively high degree of viscosity, or plasticity, are able to withstand high compressive and shear forces and thus prevent metal to metal rubbing and seizure. As stated above in the discussion of iiuid-iilm lubrication, the reason that lubricants of the fluidlm type commonly fail at only moderately high unit area pressures is due to the low viscosity possessed by the particular lubricant at the high local temperatures 'existing in the zone of greatest pressure, rather than to the fact that uidfilm lubrication is inherently impossible at great pressures. The lubricant particles which we use areA characterized by being yieldable and flowable and yet possessing a high resistance to iiow under pressure at high temperatures, and thus are able to exist in a highly viscous or plastic state between bearing surfaces under extreme-pressures and thereby support the load.

Under light load and high temperature conditions, these lubricant particles are likewise effective because of their characteristic of high viscosity or plasticity under high temperatures;

and the same, of course, holds true when both the.

between the bearing surfaces they spread toward each other to form a substantially continuous cushioning layer, as distinguished from the highly discontinuous layer formed by true solids. Hence it will be seen that the mode of lubrication effected by the type of particles employed by us somewhat resembles huid-film lubrication but differs from methods heretofore used. Under very light loads the mode of lubrication may diverge somewhat toward that of solid-particle lubrication if the .particular particles are highly resistant to flow, but the particles will still possess the property of forming a yieldable flowable load supporting layer between bearing surfaces and hence will not give true solid particle lubrication. This distinction may further be illustrated by considering the action of cork particles, which are true solids, although yieldable due to the air content.` At high temperatures cork does not possess the property of viscous or plastic flow butV remains a solid even to the carbonization temperatures, and hence gives solid-particle lu.

been used in lubricants will melt at moderatelyy elevated temperatures and will not exist in particle form, nor in a sufciently viscous state, at high temperatures, to materially increase the load carrying capacity of ordinary mineral oil lubricants with which employed or to impart a load-carrying capacity of the order with which we are concerned.

It will also be evident that our type of lubricant differs fundamentally from those containing particles which will dissolve or colloidally disperse in the vehicle at such temperatures as to prevent the sustaining of high pressures in bearings.

Ordinarily we employ a mineral oil for the vehicle. Since the vehicle is not relied upon for high-pressure lubrication, although it may exert a useful lubrication function in low pressure zones between the bearing surfaces, it may be chosen without particular regard to its lubricating quality. The principal consideration is that of the flash-point of the oil, and the oil should preferably be chosen so'that the temperature in the immediate vicinity of the bearing to be lubricated will not be above the ash-point. The vehicle should also have a sufhciently low volatility so thatundue evaporation will not take place.

We have found, for example, that a petroleum oil having a Saybolt viscosity of 100 at 100 F. gives satisfactory results when the temperatures are not high outside of -the high-pressure lubrication zones. For severe operating conditions a 1750 vis. oil may be used.

It will be understood that we are not limited tothe use of mineral oils, as any suiciently nonvolatile mobile vehicle in which the selected type of particles are insoluble comes within the scope of our invention.

The following list of substances illustrates the wide variety of organic materials which can be employed to form lubricant particles for use in mineral oil vehicles in accordance with our invention. These materials can be produced so as to be insoluble, or relatively insoluble, in mineral oil at elevated temperatures, and are highly viscous or plastic at high temperatures and pressures so -as to provide the previously described cushioning and iluid-lm eiect between bearing surfaces.

These materials may also be employed with many other vehicles, since they are of a generally insoluble nature.

Polymerized and/or oxidized drying and semidrying Uilm-Tung, linseed, and soya bean oils (and mixtures thereof) can be polymerized by heat alone to the point of insolubility in mineral oil. Castor oil can be polymerized by heating with a polymerization catalyst such as AlCls, and can be oxidized-polymerized by heating and blowing with air or oxygen.

Tung and linseed oils (and mixtures thereof) and soya bean and corn oils mixed with tung or linseed oil, can be readily oxidized at room tem.

peratures, or higher, by agitating in the presence of air or oxygen, as by blowing; preferably in the presence of an oxidation catalyst such as cobalt, manganese or lead naphthanates, resinates, ctc. These catalysts are well known in the paint and varnish art. As a modification, the oil may first be polymerized and then oxidized, or may be simultaneously oxidized and polymerized, as by blowing and agitating at elevated temperatures.

Vulcanized producir- Raw rubber; castor, soya. bean, corn, linseed and tung oils; (and mixtures thereof), can all be vulcanized, as with sulfur monochloride (szClz), to form suitable masses. The products should preferably be freed of the generated hydrochloric acid which has not passed olf, and any residual S2Cl2, since these substances will produce corrosion and wear. The pure vulcanized products of this type do not appear to cause appreciable bearing wear, although vulcanized mineral oil does, Art gum, which is a vulcanized corn oil, is a well known and inexpensive product which may be utilized.

Hydrocarbon products:-Insoluble asphalts, such as' blown or oxidized asphalt; and insoluble higher polymers of hydrocarbons, such asoxidized petroleiun resins.

Insoluble high-melting soaps:Aluminum soap of polymerized tung oil, is a soap which is insoluble and highly viscous at high temperatures and is to be distinguished from the ordinary soaps which dissolve in oil, or melt, at high temperatures.

Other materials:-Lignin, insoluble fatty acid pitches, and insoluble high-melting synthetic and natural resins and plastics, such as some coumarone-indene resins, are additional examples.

The foregoing are given by way of illustration and by no means exhaust the possible materials which can be used in accordance with our invention.

Broadly speaking, the synthetically produced products such as polymerized, oxidized and vulcanized oils, etc., may be termed reactively-thickened materials rendered insoluble and of high viscosity or plasticity at high temperatures.

'I'he products which are produced synthetically may be introduced in finely divided form in the chosen vehicle in any of several ways. They may be formed directly without the presence of the Vehicle, and then ground up and distributed in the vehicle; the raw materials may be placed in the vehicle and the product formed in situ under suicient agitation to produce nely divided particles distributed therein; or the raw materials may be placed in a liquid carrying medium, the product formed in situ in nely divided form, and the particles removed and distributed in the chosen lubricant vehicle.

An important point which should be borne in mind, vas regards the production of the synthetic products, is that the treatment must be carried Yil) to the point where the product is insoluble in the chosen vehicle. For example, when tung oil is dissolved in a mineral oil and subjected to oxidation, the oxidized product initially formed is relatively soluble in the mineral oil, but continuation of the treatment soon produces a product )which is suiilciently insoluble to cause the formation of insoluble particles.

Method of suspending particles It is, of course, desirable to secure a lubricant product, comprised of a mobile vehicle and insoluble non-colloidal lubricant particles distributed therein, which is stable and free from settling. That is, when a thick grease or paste is not desired, a more or less freely flowing product ,in which the lubricant particles are stably sussubstantially in contact with each other, a certain finite minimum force is required to produce continued relative displacement or movement of theparticles. When a mobile carrying medium contains a sufficient number of these particles, so that they are substantially in contact with each other, a certain finite minimum force is also necessary to produce continued relative motion of the particles, or to produce continued motion of other particles or bodies present. Hence a minimum force is required to produce flow or to cause a body introduced into the gel mass settle to the bottom.

This characteristic of mobile discontinuous gelatinous masses is not possessed by mobile continuous gelatinous masses, that is, gelatinous masses in which no discrete gel particles exist. In the latter case an infinitely small force will produce flow even though the gelatinous mass has a high viscosity, just as in the case of highly viscous non-gelatinous liquids. An example of a mobile continuous gelatinous mass is a solution of raw rubber dissolved in a petroleum oil. This possesses the characteristics of elasticity, stringiness and may have a high viscosity, but an innitely small force will produce flow. A gelatinous mass which has set, forming a solid jelly,

.is also a continuous gelatinous mass, but, of

course, is not mobile and exhibits the overall characteristics of a solid until broken up to form a discontinuous mass, and thus obviously until nos broken up does not possess the characteristics of a mobileI discontinuous gelatinous mass containing discrete gel particles.

The term gelcosity is used to designate this property ofdiscontinuous gelatinous masses, and

also the degree of force required to produce i'low and hence the suspending power; and the term gelcous is used to designate the discontinuous gelatinous masses possessing the property of substantially in contact with each other. Gelcose particles are, therefore, either true gel particles or particles which are similar to gel particles and have a gel nature in other words, the particles found in a discontinuous gelatinous" mass.

According to our conception, the phenomenon of gelcosity arises from one or more of the following effects: A gelcous discontinuous gelatinous mass, which may be of smooth texture and freely flowing, is comprised of at least two materials,A

forming separate phases, one of which is a liquid and one of which is inthe form of discrete coherent particles which are more or less Vsolid in consistency. These particles are swelled or solvated by the liquid, due to part of the liquid being dissolved or absorbed in the particles, or a layer or skin" of the liquid is adsorbed by the surface of each particle. Several or all of these effects may occur as regards a single particle.

These composite gel-like particles possess elasticity and resiliency. In the case of true gel particles this is the same property that is a Well known characteristic of large gel masses which have set. An adsorbed liquid layer or skin may also produce elastic behavior, even through the kernel is not elastic in nature, due to the tension ofthe outer surface of the adsorbed layer or of what may be termed the interface between the adsorbed liquid and the unadsorbed liquid which surrounds it. These elastic particles resist and restrict deformation, with the result that a nite force is required to produce motion of one particle through the surrounding particles and likewise to produce motion of any other object through a mass of such particles, provided that the particles are close enough together so that they cannot be merely carried through the liquid without iniluencing each other. Another eiectis also obtained, we believe, when particles having adsorbed liquid skins are so close together, as regards distance between nuclei, that a single adsorbed liquid skin surrounds several nuclei. In this case separation of the particles is restrained, because such separation tends to increase the area of the outer surface of the adsorbed liquid, and thus tends to increase the surface energy. There is always a tendency for a body to resist increase of surface energy, and to change in such a way as to decrease the surface energy. This is illustrated by the well known fact that a drop of liquid resists partition, and if distorted seeks to assume a formv which will give it `a lesser surface area. Hence, separation of the nuclei is restrained, and the nuclei tend to. snap back together when separated. The result is that a minimum nite force is required in order to produce continued motion.

The behavior of gel particles subjected to prodding has been observedA under a microscope, and they act 1in the manner described above, so that, irrespective of theory, there appears to us to be no doubt of their possessing the characteristics above set forth.

The gelcous mass may, therefore, be spoken of broadly as a discontinuous gelatinous mass composed of elastic particles substantially in contact with each other and,I having the interspaces containing a liquid.

Gelcous mixtures have been made up which indefinitely resist settling of the particles contained therein, both as to the gelcose particles and as to non-gelcose particles distributed therethrough. This is due to the fact that the force exerted upon each particle by gravity is insumcient to produce continuous motion through the surrounding particles, resulting in an equilibrium condition in which the particles are stably suspended, notwithstanding that the mixture may be freely flowing and pour readily from a container in the manner of a light oil. Broadly speaking, suspended non-gelcose particles present may be said to be supported by the gelcose particles.

Other types of particles also exhibit the property of a minimum force requirement for displacement, but behave diierently than particles of a gel nature. Gelcose particles may be used in much smaller number, and a much smaller amount of material from which they are formed may be used, due to the swelling, solvation or adsorption which occurs and which greatly increases the individual sphere of action of the particles and gives a greater bulk eifect. It is only natural that most kinds of vparticles which 20 are in contact with each other will require a force to overcome the rest friction, that is, the stiction eiect. This characteristic is not su'icient to account for the phenomenon of gelcosity exhibited by gel-like particles of an elastic nature.

The relative gelcosity or suspending power of mobile media may be easily determined by using a light metal plate or vane suspended in a vertical plane by a ne wire or fibre secured to a iixed support. The wire should be surrounded by a 30 fixed tube or sleeve to prevent sway. The vane is placed in the medium and the latter rotated a certain amount, as by turning the receptacle, whereupon the Vane will swing about its axis and then return toward its initial rest position, due to the restoring force exerted by the wire. If the medium is gelcous the vane will not return completely but will come to rest in a displaced position, the greater the displacement the greater the force needed to cause continuous movement within the medium and, hence, the greater the gelcosity or suspending power. If the medium is mobile but continuous, the vane will slowly return to the initial position even .though the medium is highly viscous; while a highly gelcous medium will cause a large displacement even though quite freely owing'in consistency. It will be found that particles of a non-gelcose nature must be present in very large concentration to produce any noticeable displacement, whereas particles of a gel nature cause a deiinite displacement even when produced by a relatively small concentration of the material which is solvated, swelled or surrounded by adsorbed liquid, to form them. Hence it is possible to determine whether the particles are gelcose and the relative gelcosity imparted by various kinds and concentrations of gelcose particles.

Gelcose lubricant particles may be made from the following in accordance with our invention: Oxidized, polymerized or vulcanized tung oil, and combinations thereof; vulcanized corn oil; vulcanized linseed oil; vulcanized rubber; and mixtures thereof. These are given by way of illustration and we are not limited thereto. From all of these materials freely-flowing lubricants comprised of lubricant particles stably suspended in a liquid vehicle may be prepared.

There are two principal ways of producing gelcose particles from the material. The iirst method consists in preparing the material directly and subsequently grinding it in powdered form with a liquid capable of solvating or swelling it without dissolving it, and then distributing the gelcose particles in a suitable liquid Vehicle, which maybe the same or a different liquid substance.

'Ihe second method used by us, and the one which weprefer, is to dissolve the raw material in unthickened form in a liquid in which the thickened form is insoluble and which is capable of imparting gelcosity to particles of the thickened material. This liquid may or may not be the ultimate vehicle for the particles. We prefer to form the particles in situ in the ultimate vehicle in which the particles are employed in lubrication use.

The following illustration will make this second method clear: of tung oil is dissolved in a petroleum oil, such as a light neutral oil of 28 Baume gravity, with a small amount of an oxidation catalyst preferably added, and subjected to blowing or other method of producing oxidation and agitation of the tung oil. After the oxidation has progressed for a certain period, an in'- soluble oxidized tung oil product will come out of solution. Due to the agitation it will be in the form of small particles and these particles will become solvated or swelled by the mineral oil and thus become gelcose particles. Thus three step's are involved-(a) dissolving the tungV oil in a solvent, (b) changing the state of the tung oil so that it comes out of solution, (c) dissolving, absorbing or otherwise causing some of the original solvent to be taken up by the tung oil in its new state so as to form a gel, and (d) breaking the gel up so as to produce a discontinuous gelatinous mass containing discrete gel particles. Long continuation of the oxidation will eventually result in particles of less and less gelcosity, andY this is probably due to the tung oil becoming oxidized to a point where its capacity for taking up the solvent is diminished.

These methods of producing gelcose lubricant particles are illustrated in greater detail in th subsequent examples.

As previously stated, an auxiliary material may be used to produce gelcose particles for sustaining non-gelcose lubricant particles, or lubricant particles of a gelcose nature but not completely self-sustaining due to the low concentration in which used.

For example, various soaps or waxes insoluble in the Vehicle at room temperatures may be used. As an illustration of this, aluminum stearate or sodium oleate may be dissolved in a mineral oil, by heating together, allowed to cool to form a gel, and agitated to produce nely divided'gel particles. 'Ihe lubricant particles are distributed through the mixture and sustained by the gel particles.

Carnauba wax may be used very eiectively for this purpose, as described and claimed in our copending application, Serial No. 700,005, led August 15, 1934. Its use is illustrated in Example 4.

Gelcose lubricant particles, of the type with which our invention deals, retain gelcosity at high temperatures due to the fact that the lubricant material used is of a character which does not melt or dissolve at high temperatures.l This property is not possessed by the ordinary soap and wax gels, and these lose gelcosity at various moderately ele'vated temperatures. In most cases this does not impair their practical utility for suspending lubricant particles, for the reason that during use of the lubricant mixture there will be suicient agitation and circulation to prevent settling out of the lubricant particles and to maintain a uniform mixture, and upon standing during idling the gelcosity will be restored due to the lowering of the temperature.

With many gelcous mixtures a serum layer will form, due to contraction of the gel mass, unless suiiicient gel material is present to exist in equilibriumwith the liquid phase. This may be due to either or both of the following effects: 'I'he gelcose particles, which in most cases are denser than the liquid vehicle, will tend to settle until substantially in contact, further settling then being prevented by the gelcosity property, leaving a supernatant serum layer of the liquid; unless the particles are originally present in such concentration as to be substantially in contact. Even when substantially in contact, the individual gel particles will tend to contract, with a resultant exuding of part of the liquid contained therein, until an equilibrium is established, if they have originally taken up too much liquid. This latter effect is known as syneresis.

Hence if a mixture is desired which will remain substantially uniform on standing, suflcient gelcosity producing material should be employed initially; or as an alternative the mixture can be allowed to stand until substantial equilibrium has resulted and the serum layer then drawn oi.

The formation of a serum layer does not mean that the gelcose particles are not stably suspended, but that an excess of liquid is present. In other words, there is no settling to a compact mass, and the mixture can be easily made uniform by stirring.

In most cases the formation of a serum layer and especially a relatively thin one, upon standing, is unobjectlonable even in a bearing box, since motion of the bearing parts will quickly produce uniformity and in many cases the actual bearing surfaces will be below the serum layer at all times.

Method of testing A special machine has been developed for testing our lubricants and making comparisons with various existing types.

In this machine three steel balls of the same diameter are clamped in a vertical chuck in such a way that they are in contact with each other and their top points define a horizontal plane. The balls (termed statorv balls) are restrained from all motion except about the common central vertical axis of themselves and the chuck. A fourth ball (termed rotor ball) is mounted above the others in another vertical chuck, on the same central axis, and arranged for rotation by means of an electric motor. This upper ball is restrained from vertical motion, and the chuck holding the lower balls is arranged so that it may be moved upwardly to bring the upper ball in three point contact with the three lower balls. By applying ,upward pressure against the lower chuck, as by means of a hydraulic piston, the upper ball can be rotated against the lower balls under various loadings. A cup, mounted on the lower chuck and extending around the balls, is used as the con;- tainer for the lubricant to be tested. The lower chuck is mounted on ball bearings so that it is free to turn, and by measuring the force required to hold it stationary, the torque produced by the rotation of the upper ball against the lower balls can be determined.

Steel balls manufactured for use in ball bearings are used. These can be readily obtained of a high uniformity as regards diameter, smoothness, and metal hardness. A new set of balls is used for each test. In the tests reported herein, the lower balls were each of carbon steel and inch diameter, while the upper ball was of chrome steel and 1/2 inch diameter. The upper ball was rotated at a speed to give a bearing contact velocity of 200 feet per minute.

The lubricant container, or cup, used in thev ,indication of behavior under severe service conditions was obtained.

The usual test procedure was to place a. new set of balls in the chucks, iill the `cup with the lubricant to be tested, start the upper or rotor ball rotating, raise the lower of stator balls until in bearing contact with the rotor ball, rapidly increase the total load up to the selected top value, hold the load for the desired length of test, and remove the load. During the period of increasing load the torque indicator is watched for signs of seizure .between the bearings. 'I'he total load that can be useddepends upon the quality of the lubricant.

Following the test, the balls are removed an examined for signs of corrosion and undue wear. When good lubrication has occurred, the central ball will be relatively free from signs of wear and the stator balls will each have a small smooth concave depression, or crater, with an elliptical boundary. Each stator ball is placed under a measuring microscope and the dimensions of the boundary outline of the cratermeasured, and

the enclosed plane area computed. This area,

termed the effective area of bearing wear, is the projected area of the worn surface on a plane tangent to the ball at the original point of contact, and represents the area bearing the 1 component of total load per ball which is perpendicular to the ball at the original point of contact. When the total load per ball (which is one-third the total measured vertical pressure exerted between the rotor and stator balls) is multiplied by a constant, due to the angularity of contact, to give the component perpendicular to the eifective area of bearing wear, and is divided by this eifective bearing area value, the sustained bearing pressure per unit area is obtained. This is equal to the result which would be obtained by integr-ating the component of pressure perpendicular to each point on the surface of the crater over the whole surface and dividing by the actual area of the crater surface.

The figures given herein for load are lthose of the component of total load per ball perpendicular to the effective area of bearing wear, and

represent the effective load on the eifective area of bearing wear. The figures given for effective area of bearing wear are the average values per ball as determined from all three stator balls. The unit area pressure, which represents the load-carrying capacity of the lubricant at the end of the test, is obtained by dividing the load by the effective area of bearing wear.

It has been found that the load per ball should be about 50 pounds per square inch or greater in order that substantially all of the load will be carried by the area of bearing wear, thus giving accurate results. If a much lower load is used, a substantial percentage of the load will be carried by the lubricant film in the annular region surrounding the area of wear. thus making the calculation of load-carrying capacity inaccurate.

During the test, the bearing area will increase so long asthe unit area pressure is above the stable load-carrying capacity oi the lubricant, until a point of equilibrium is established if the test is continued long enough, assuming that a nonabrasive non-corrosive lubricant is used. Experience has shown that a good lubricant which is not abrasive or corrosive in nature will have a stable load-carrying capacity as shown by a fteen minute test run.

Other points regarding this test procedure, and the interpretation of results, will be given in connection with the tests reported below. This test machine and method were developed, and are described in some detail here, because available machines were unsuitable for our purpose. The present machine and procedure make possible the use of high loads, quick testing, only small lubricant samples are needed, and data is obtained which is of practical significance. The results are comparable with equivalent data from 'other known test methods.

Comparative tests In order in indicate the load-carrying capacity and other characteristics of certain typical known lubricants of the prior art, to aord a basis of comparison both as regards the performance given hereafter for our type of lubricant, and of the test method used by us, tests were run as follows:

(a) A light petroleum neutral oil, of 28 Baume gravity and Saybolt viscosity of at 100 F., was sulfurized by heatingl with 5% of SzClz until there was no further noticeable evolution of hydrochloric acid gas. This -is a sulfurized type of oil and is regarded as having a very good highpressure lubrication capacity. A load of 58 pounds (as defined above) was applied, the pressure being raised to the top value during a period of about 30 seconds, and the load then held constant for 15 minutes.

At the end of the test the relative torque was 13 (relative values being given herein as these fully indicate comparative characteristics), the eiective area of bearing wear was 0.0095 in?, and the load-carrying capacity was 6,150 lbs./in.2. The bearing areas were very irregular in shape, indicating pronounced seizure during the development of the areas, and the central or rotor ball was deeply scored. This deep scoring of the rotor ball was probably due to work hardening of the stator balls as a result of execssive temperatures developed, caused by the poor lubricating quality of the sulfurized oil, whereby the stator balls became hard enough to abrade and cut the originally harder rotor ball. I'his test shows that the presence of sulfur in available reactive form causes high corrosion and wear of bearing surfaces and also a high degree of friction and torque.

The use of a higher total load was not feasible due to the pronounced seizure which would have resulted.

(b) 100% monochlornaphthalene was used without any other ingredient, as the lubricant. This is an example of a chlorinated oil.

The same procedure and load of 58 lbs. was used as before and the following indications obtained: The relative torque was 6.3, the eiective area of bearing wear was 0.00304 in?, and the load-carrying capacity was 19,000 lbs./in.2. This represents a very good perfomance according to present standards, but the lubricant could not generally be used in this concentration, due to its volatility, odor, etc.

EIampleS The following examples illustrate the nature and performance of our type of lubricant, and in two of the examples the data is indicated by curves shown in the accompanying drawing, wherein- Fig. 1 shows a curve indicating the performance of oxidized tung oil mixed with mineral oil. for various periods of oxidation time, as described in Example 1; and

Fig. 2 shows performance curves for oxidized tung oil, and for sulfurized mineral oil, indicating the individual and relative performances for various loadings, as described in Example 2.

Example 1 10% of tung oil was dissolved in 90% of a light petroleum neutral oil (28 Baum, Saybolt viscosity of 100 at 100 FJ. An oxidation catalyst consisting of cobalt naphthanate was added, in an amount of produce a 0.05% content of cobalt.

One portion was used for a zero oxidation-time test, and the remainder was placed in a con tainer. A small gear pump was arranged with connecting lines to pump the liquid from the bottom of the container to a discharge opening situated several inches above the surface. The discharge of the liquid in a stream upon the surface produced considerable agitation and bubbling, whereby the entire body of liquid was continuously circulated, agitated, and exposed to contact with air. No external heating was used, but as no special cooling was resorted to in this case, some internal heating occurred due to the heat of oxidation of the tung oil and the work done by the pump, so that a temperature of about F. was developed by the end of the whole run. At various time intervals samples were removed and tested. While a certain amount of polymerization may have been produced as a result of the agitation and slight heating, the tung oil was predominately oxidized.

The test procedure was as previously described. The load in each case was raised to a. 77 lbs. top value during a period of 30 seconds, and this load was then maintained constant for 15 minutes. The area developed on the rotor balls was measured and the sustained bearing prsure per square inch, at the end of the test, computed.

The curve of Fig. 1 shows the pressure ,per square inch, sustained at the end of a fifteen minute test period, plotted against t'he oxidation time. It will be seen that the load-carrying capacity of the tung oil-mineral oil mixture slowly increases from about 8,5100 to 12,500 iba/in,2 during the rst 60 minutes of oxidation, following which a very sudden transition occurs, resulting in a` load-carrying capacity of 76,000 lbs./in.2 at the end of an additional thirty minutes, and from this point on rthe load-carrying capacity remains substantially constant.

During the iirst 60 minutes of oxidation the mixture remained clear or but slightly opalescent, showing that suiiicient oxidation had not yet occurred to produce an appreciable concentration of insoluble oxidized tung oil material. The increase of load-carrying capacity during this period is attributable mainly to the increasing amount of oxidized tung oil in solution, and perhaps to gelcity and quantity of gel present, and inl creasing load-carrying capacity. From this point on the load-carrying capacity remained substantiallyconstant at '76,000 lbs/in?, notwithstanding a further increase of gelcosity.

This very sudden transition to an entirely different order of magnitude of load-carrying capacity, commencing with the first sign of gel formation, very clearly demonstrates that it is` the gel material itself which is responsible for the very high pressure sustaining capacity of the gelatinous product, and that the mineral oil vehicle and dissolved oxidized and unoxidized tung oil are entirely incapable of producing'this result. The transition is altogether too rapid to justify any inference that the presence of the gel particles is unimportant and that it is the increase of tung oil oxidation, as such, which is responsible for the effect.

This is further borne out by an interesting experiment which was made. A portion of a sample, taken just after gel formation commenced, was allowed to stand overnight, during which time the gel material settled to the lowefr third of the container as the result of its low concentration. The bulk of the supernatant serum layer of oil was poured off and the remaining gel mass thoroughly stirred, and tested. The test showed a load-carrying capacity close to the 76,000 lbs/in.2 top obtained in the tests on the more highly oxidized samples.

This experiment also shows that during the transition period the increase of load-carrying capacity is primarily due to the increase of gel concentration, rather than to an effect caused by the increasingly oxidized state of the tung oil contained in the gel particles.

v The fact that the load-carrying capacity re- ,mains substantially constant after the rapid transition period has passed, indicates that a certain concentration of gel is sufficient to maintain lubrication at a limit imposed by the nature of the particular type of gel particles, and that additional particles per unit volume do not function to materially alter the effect.

The foregoing brings out the essential lubrieating characteristics of the lubricant particles employed by us and shows that the kind of lubrication obtained, and hence the nature of our type of lubricant differs in kind and not merely in degree from lubricants employing related materials in solution or other state different from that which we use.

In the production of oxidized tung oil lubricants for commercial use we would preferably carry the oxidation further than 'is described in this examplein order'to reach a substantially stable state, so that no surface skin will be formed on the lubricants when they are exposed to the atmosphere, and in order to obtain a greater gelcosity and self-sustaining power of the gel particles.

AExample 2 (a) Anoxidized tung oil type of product was made up in accordance with our invention in the manner described in Example 1, except that the oxidation time was extended to about 6 hours. As 10% of tung oil was used, the product was quite gelcous in nature and but little serum separaiedfrom the solvated oxidized tung oil particles upon standing. The lubricant mixture was free ilowing in consistency. The agitation had been sufficient to make the mixture smooth in texture, that is, free from gel particles of large enough size to be detected by the eye. These particles were, however, plainly visible under a. microscope.

Rfegular minute tests were run at various loads, ranging from 11 to 90 lbs. per stator ball. In each case the load was applied rapidly to the selected top value and the latter then held constant for the 15 minute test period.

In Fig. 2 the full-llne-curves show for this lubricant: (I) the eiective area of bearing wear, (II) the apparent sustained bearing pressure obtained by 'dividing the load by the eiective area of bearing wear, ,and (III) the relative torque; all taken at the end of the test.

It will be noted that the bearingI pressure curve shows a decrease from about 90,000 lbs./in.2 at the lightest load to about 76,000 lbs./in.2 at the heavy loads. The curve approaches a horizontal line and at loads above 50 lbs. is substantially constant in value.

The apparently greater value at low loads, which is characteristic of all lubricants, is believed by us to be due to the following: When two bearing surfaces approach each other tangentially, as is the case with two balls, there exists a substantial zone of near-contact adjacent to the point or line of greatest approach, and in this zone the pressure is less. A liquid present in this adjacent region is capable of supporting part of the total load by iluid-film lubrication, and when the load is 10W enough the load may be so substantially supported as to prevent appreciable wear of the bearing surfaces. In the latter case, little or no area of Abearing'wear will develop during an ordinary test period and hence y an infinite load-bearing capacity would be computed by dividing theload by the area of wear. Obviously this is a mere pseudo capacity, and results from ignoring the fact that the load is not carried in the zero-contact area but by the fluidlm in the surrounding region. As the load is increased, a point is reached where the uid-lm ycannot support the load, and beyond this point wear will take place rapidly until an area has developed which will support the load with the y given lubricant. At the same time, the develop- .pacity will be masked, and the apparent capacity determined by the test method will be too high. It is therefore necessary to apply a sufliciently high load if a true load-bearing capacity is desired.

Curve I shows that 76,000 lbs./in.2 is a true value for the load-carrying capacity of the oxidized tung oil lubricant, since at above 50 lbs. load no appreciable decrease occurs upon further increase of cad.

It will also be noted that the eil'ective area. of bearing Wearcurve, and the torque curve, are straight lines, showing that both increase directly as the top load and that the lubricating action is, therefore, uniform at various loads.

(b) For comparison purposes, similar tests were run on a prior art type of sulfurized oil comprised of alight petroleum neutral oil treated With 11/% S2012. This lubricant is representative of lubricants containing sulfur in availably reactive form. Corresponding curves, in brokenline, are shown in Fig. 2.

The most striking characteristic is shown by the area of wear curve, which increases with great rapidity, indicating that the lubricant has so little extreme-pressure lubricating quality as to produce little support under loads sufficient to .cause rubbing contact. An examination of the test balls showed that irregular areas were developed in the stator balls, and that at the higher loads a roughened surface was produced together with an annular depression abraded in the rotor ball, indicating the development of high temperatures and stresses.

'I'he apparent sustained pressure curve shows a very rapid falling off with increase of top load, reaching a value of about 5,500 lbs./in.2 at`58 lbs. It will also be noted that the torque curve increases much more rapidly than is the case of our oxidized tung oil lubricant.

At low loads the extrapolated values are good, but, as pointed out above, at these low loads extreme-pressure lubrication does not actually take place', or is outweighed by the lubricating eiect in the low pressure zone. This clearly demonstrates that the behavior of lubricants at low pressures is not a reliable indication of the capacity for extreme-pressure lubrication, and also that adequate loads must be used to obtain re- 40 liable perfomance data for eXtreme-pressure conditions.

Example 3 A solution of 25% of tung oil in 75% of a light petroleum neutral oil was oxidized in the presenceof a catalyst, in the manner previously described, for a period of 5 hours. At the end of two months standing the product was uniform and free from any serum layer, and appeared 5 stable and free from signs of the skin which is produced by oxidation during standing. It had the consistency of a light grease, but upon stirring quickly became freely flowing.

Two tests were run, both under a top load of 90 lbs., and in each case the load was built up during a period of 90 seconds.

In the first test the top load was maintained for only 30 seconds and the test then stopped. The eiective area of bearing was 0.000616 in?,

giving a sustained bearing pressure value of 60 142,000 lbs./in.2, and the relative torque was 7.5.

Since a high load was used, the 142,0001bs./in.2 value truly indicates the actual load-bearing capacity at the end of the 30 second period. This value is all the more extraordinary when it is I realized that it does not represent the mere instantaneous value obtained in the type of test where pressure just before seizure is measured, `but represents-a pressure which can be carried 0 for a. short period Without seizure occurring. Un-

doubtedly the pressure before seizure value would be much higher.

'Ihis is not, of course, the stable load-carrying capacity. 'I'he pressure is such that fairly 75 rapid wear will occur until an. area has been de- Veloped which will permit the lubricant to support the load without further appreciable wear.

In tests described in the foregoing examples,

the load-carrying capacity at the end of 15 minutes test was used to obtain the stable capacity. In order to check this, a second test was made of the same lubricant, under the same load and rate of loading but for a period of 65 minutes instead of 30 seconds.

At the end of this test period the main body of lubricant in the cup had a temperature of 374 F. (190 C.), which was 24 F. above the ashpoint of the petroleum oil vehicle, resulting from the small sample and lack of provision for special cooling. Nevertheless, the relative torque was only 8, the effective area of wear was 0.00123 in.2 and the sustained pressure was 73,000 lbs/in?.

This second test indicates that the lubricant holds up under very severe operating conditions. Furthermore, the load-carrying capacity was the same as previously described in connection with 15 minute test periods, within the limits of accuracy of the test.

In view of the performance dataldescribed and discussed in the foregoing examples, and other data omitted for lack of space, we believe ourselves fully justied in setting the stable loadcarrying capacity of the particles of oxidized tung oil solvated with mineral oil at close to 76,000 1bs./in.2, as a conservative figure. We believe that this capacity is unprecedented as regards lubricants of any type and clearly shows that our type of lubricant makes possible a pressure-range of lubrication heretofore unapproached. As previously pointed out in some detail, the particles used by us produce what we believe to be essentially iiuid-lm lubrication.

Eample 4 This example illustrates the use of lignin for the lubricant particles, in accordance with our invention, and also the employment of auxiliary material to impart gelcosity or suspending power to the lubricant mixture for supporting the lubricant particles in a mobile vehicle.

'Ihe vehicle used was a light petroleum neutral oil (28 Baum, 100 vis. at 100 FJ. 71/% of carnauba wax was dissolved in a portion of the petroleum oil at 100 C., and the solution was then allowed to cool to below C., and stirred to produce a smooth gelcous mass which was freely flowing. The mixture was diluted with additional petroleum oil to produce a wax content of 3%, after. which 5% of powdered lignin was introduced and the whole thoroughly stirred to produce a uniform product. This lubricant remained uniform on standing, as the wax-oil gel particles"imparted suiiicient gelcosity to prevent settling of themselves and of the lignin particles.

The lignin particles in this lubricant mixture are not gelcose, and hence not self-sustaining, but do possess the general characteristics of our type of lubricant, namely, they are capable of highly viscous or plastic flow at high temperatures and make possible lubrication at a higher order of magnitude of unit area pressure than is possible with the vehicle alone.

The usual test was run, with a top load of 68 lbs. quickly applied and then held constant for 15 minutes. 'I'he eiective area of bearing wear was 0.0011 in?, the load-carrying was 61,000 lbs/in?, and the relative torque was 5.

Example 5 'I'his example illustrates the use of gelcose equal volume of carbon tetrachloride, the latter serving merely as a diluent to prevent excessive heating during the subsequent reaction, and sulfur monochloride (S2012) in amount equal to 16%% by weight of the corn oil was then added. Vulcanization occurred and the product was a rubbery translucent mass. This was divided into small pieces and boiled in several washings of water to remove soluble material present, such as hydrochloric acid formed by the reaction, and to evaporate the carbon tetrachloride. The puried product was then dried to about 150.F. until again translucent and free from moisture.

A quantity of this purified vulcanized corn oil was crushed to a powder and ground in an equal volume of petroleum oil (neutral oil 28 Baum, 100 vis. at 100 F.) for 15 hours. Additional oil was then added to dilute the lubricant' to a 7% content of the vulcanized corn oil. The resulting lubricant was free iiowing and yet possessed of some gelcosity due to the swelling or solvation of the particles.

A test was run with a top load of 77 lbs.I

quickly applied and then held for 15 minutes. The effective area of bearing wear was 01000903 in?, lbs/in?, and the relative torque was 6.7.

The sharp differentiation between the type of lubricant particles which we employ and ordinary oils, waxes, soaps and greases, which melt and become quite uid at only moderately elevated temperatures, is illustrated by the following experiment. A quantity of finely divided vulcanized corn oil, prepared in the manner indicated above, was subjected for ten minutes to a temperature'of 190 C. under a pressure of 12,000 pounds per square inch, in .a hydraulic press. At the end of the test, the particles of vulcanized corn oil not only had not melted but they had not become fused or stuck together. This was a severe test, since both the temperature andfpressure were high. The same test was given to finely divided oxidized tung oil particles, prepared in the ,man-

. ner described, with the same results. Such particles are in fact non-melting, meaning that they do not melt at temperatures below the decomposition point, and also remain undissolved in petroleum oil and other vehicles at these high temperatures.

From the foregoing description, discussion and examples'it will be apparent that we have developed a. new type of lubricant which differs fundamentally in its conception and nature from prior forms, and makes possible a new standard of performance. We have given in some detail the theory of operation which we believe applies, in order that those skilled in the art may be guided toward the various specific materials, other than those named herein, which come within the scope of our invention, and so that the most `effective use may be made'of them; but we do not intend to be limited thereby.

It will be evident Athat a wide choice of materials is afforded, permitting selection of lubricants best fitted for particular purposes, but that the general characteristics of all of the lubricants coming within the scope of our invention make possible very effective lubrication at high-temperatures and/or high pressures in all cases.

Certain particular lubrication fields have althe load-carrying capacity was 85,000A

ready been indicated as being especially in need of betterextreme-pressure lubricants. Among other lubrication fields in which our, lubricants are of especial value may be mentioned the following, by way of illustration: The lubrication of roll-neck bearings in steel mills, where both high general temperatures and high pressures are a great problem; lubrication of thrust bearings of large turbines, dynamos, etc.; vthe lubrication of all bearingairrespective of pressures, located in high temperature regions such as in and near ovens and furnaces; and the lubrication in metal-cutting where the chips bear against the cutting tool with great pressure and/or where considerable heating results, as in turning, drilling,l milling and thread cutting. Many other advantageous applications of our lubricants will occur to those skilled in the art.

Other types of lubricant may, of course, be mixed with the present type of lubricant as circumstances may direct. For example, a noncorrosive lubricant especially adapted for low pressure use may be added to meet conditions calling both for the best low-pressure low-temperature and high-pressure and/or high-temperature composite lubricant.

` Even in the relatively low-pressure low-temperature field, many of our lubricants may be used to advantage by virtue of the adhesive and protective qualities possessed, as for example the oxidized tung oil. Such lubricant material will cling to the bearing surfaces during idling and following shut down, and thus cause good lubrication immediately upon starting, even as to surfaces lubricated by the splash method.

In the claims it will be understood that the term fmobile refers both to high and low viscos.

that the term petroleum includes equivalentA mineral and hydrocarbon oils.

Having disclosed a number of embodiments of our invention for purposes of illustration, and our conception of the underlying theory and mode of functioning, but without any intent to be limited thereby, what we claim is as follows:

1. A lubricant comprising a non-volatile mobile vehicle, and finely divided highly viscous particles of greater than colloidal size distributed therethrough as a lubricant ingredient and essentially composed of drying or senil-drying oil reactively-thickened to the point of insolubility in mineral oils at high temperatures, the vehicle being of a kind in which the particles are undissolved at both ordinary and high temperatures and the lubricant mixture being able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form even at high temperatures of at least about 190 C.

2. A lubricant comprising a non-volatile mobile vehicle, and nely divided highly viscous particles of greater than colloidal size distributed therein as a lubricant ingredient and essentially composed of oxidized or oxidized-polymerized oil from the group consisting of tung, linseed, corn, soya bean and castor oils, the oil being reactivelythickened to the point of insolubility in mineral oils at high temperatures, the vehicle being of a kind in which the particles are undissolved at both ordinary and high temperatures and the lubricant mixture being able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form at high temperatures.

3. A lubricant comprising a non-volatile mobile vehiclel and nely divided highly viscous particles of greater than colloidal size distributed therein as a lubricant ingredient and essentially composed of vulcanized oil from the group consisting of tung, linseed, corn, soya bean and castor oils, the oil being vulcanized to the point of insolubili'ty in mineral oils at high temperatures, the vehicle being of a kind in which the particles are undissolved at both ordinary and high temperatures and the lubricant mixture being free of corrosive material and able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form at high temperatures. v

4. A lubricant comprising a non-volatile petroleum oil vehicle, and finely divided highly viscous particles of greater than colloidal size distributed therethrough as a lubricant ingredient and essentially composed of drying or semi-drying oil reactively-thickened to the point of insolu- 25 bility in the vehicle at both ordinary and high temperatures, the lubricant mixture being able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form even at high temperatures of at least about 190 C.

5. A lubricant comprising a non-volatile petroleum oil vehicle, and finely divided highly viscous particles of greater than colloidal size distributed therein as a lubricant ingredient and essentially composed of oxidized or oxidizedpolymerized oil from the group consisting of tung, linseed, corn, soya bean and castor oils, the oil being reactiVely-thickened to the point of insolubility in the vehicle at both ordinary and high `i0 temperatures, the lubricant mixture being free of corrosive material and able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form at high temperatures.

6. A lubricant comprising a non-volatile petroleum oil vehicle and finely divided highly viscous particles of greater than colloidal size distributed therein as a lubricant ingredient and essentially composed of vulcanized oil from the 50 group consisting of tung, linseed, corn, soya bean and castor oils,'the oil being vulcanized to the point of insolubility in the vehicle at both ordinary and high temperatures, the lubricant mixture being free of corrosive material and able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form at high temperatures.

7. A lubricant comprising a non-volatile mobile vehicle and finely divided highly viscous particles 60 oi' oxidized tung oil of greater than colloidal size distributed therein as a lubricant ingredient, the tung oil being oxidized to the point of insolubility in mineral oils at high temperatures, the vehicle being of a kind in which the particles are undis- 65 solved at both ordinary and high temperatures and the lubricant mixture being able to sustain extreme bearing pressures owing primarily to the presence of said particles in highly viscous form at high temperatures.

8. A lubricant comprising a non-volatile petroleum oil vehicle and iinely divided highly viscous particles of greater than colloidal size of oxidized tung oil solvated with petroleum oil and insoluble in the vehicle, said particles being un- 7 5` dissolved and highly viscous at high temperatures and serving as a lubricating ingredient capable of sustaining extreme bearing pressures.

9. A freely flowing lubricant comprising a petroleum oil vehicle and nely divided particles of greater than colloidal size of oxidized tung oil formed in situ and solvated by the vehicle so as to constitute therewith a freely flowing discontinuous gelatinous mass containing suspended lubricant gel particles, the particles beingr oxidized to the point of being undssolved and highly viscous in the vehicle at high temperatures and serving as a lubricant ingredient capable of sustaining extreme pressures. 10. A lubricant comprising a non-volatile mobile vehicle and iinely divided highly viscous particles of vulcanized corn oil of greater than colloidal size distributed therein as a lubricant ingredient, the corn oil being vulcanized to the point of insolubility in mineral oils at high temperatures, the vehicle being of a kind in which the particles are undissolved at both ordinary and high temperatures and the lubricant mixture being able to sustain extreme bearing pressures o'wing primarily to the presence of said particles in highly viscous form at high temperatures.

11. A lubricant comprising a non-volatile petroleum oil vehicle and finely divided highly viscous particles of greater than colloidal size of vulcanized corn cil solvated with petroleum oil and insoluble in the vehicle, said particles being undissolved and highly viscous at high temperatures and serving as a lubricating ingredient capable of sustaining extreme bearing. pressures.

l2. A freely iiowing lubricant comprising a petroleum oil vehicle containing suspended nely divided particles of greater than colloidal size of vulcanized corn oil solvated by the vehicle and present in amount to serve as an extreme-pressure lubricating ingredient but not to prevent free ow, the particles being vulcanized to the -point of being undissolved and highly viscous in the vehicle at high temperature.

13. A lubricant comprising a non-volatile mobile vehicle and iinely divided particles of lignin of greater than colloidal size distributed therein as a lubricant ingredient, the vehicle being of a kind in which the particles are undissolved and highly viscous at high temperatures.

i4. A lubricant comprising a non-volatile petroleum oil vehicle containing finely divided particles of lignin of greaterthan colloidal size present in suicient amount to serve as a lubricating ingredient.

l5. A freely flowing lubricant comprising a non-volatile petroleum oil vehicle gelled with an elastic-gel-forming material so as to contain iinely divided elastic gel particles substantially in contact with each other and .having the interspaces containing oil, constituting a freely :liowing suspending medium, and finely divided particles of lignin of greater than colloidal size distributed through the mixture in amount to serve as a lubricating ingredient and yet be suspended by the gel particles.

16. Amethod of providing lubrication in a zone in which high temperature conditions prevail comprising supplying into the zone and maintaining thereln a lubricant containing a, nonvolatile mobile vehicle and containing finely divided highly viscous lubricating particles of greater than colloidal size essentially composed of oxidized or oxidized-polymerized oil from the group consisting of tung, linseed, corn, soya bean and castor oils, said particles being of a kind lti highly viscous and insoluble rin the vehicle even at high temperatures in excess of about 190 C.

17. A method of lubricating bearing surfaces and the like comprising applying to said surfaces a petroleum oil vehicle containing oxidized tung oil in the form of finely divided particles of greater than colloidal size present in amount to serve as a. lubricating ingredient, said particles being of a kind undissolved and highly viscous in the vehicle at high temperatures.

18. A method of providing effective lubrication in a zone in which high temperature conditions prevail comprising supplying into said zone and maintaining therein a lubricant containing a non-volatile mobile vehicle and containing finely divided highly viscous lubricating particles of greater than colloidal size essentially composed *of vulcanized oil from the group-consisting of tung, linseed, corn, soya bean and castor oils, said particles being of a kind highly viscous and insoluble in the vehicle even at high temperatures in excess of about 190 C.

19. A method of lubricating bearing surfaces and the like comprising applying to said surfaces a petroleum oil vehicle containing vulcanized corn oil in the form of finely divided particles of greater than colloidal size present in sufficient amount to serve as a lubricating ingredient, said particles being'of a kind undissolved and highly viscous in the vehicle at high temperatures.

20. A method of providing eiective lubrication in a zone in which high temperature conditions prevail comprising supplying into said zone and maintaining therein a lubricant containing a non-volatile mobile vehicle and containing nely divided lignin particles of greater than colloidal size in amount to serve as a lubricating ingredient.

21. A method of lubricating bearing surfaces and the like comprising applying to said surfaces a petroleum oil vehicle containing finely divided lignin particles of greater than colloidal size in amount to serve as a lubricating ingredient.

VICTOR R. ABRAMS. CARROLL A. HOCHWALT. 

